Overview
In this blog post, we delve into CVE-2011-10018, a severe cybersecurity flaw discovered in myBB version 1.6.4. This vulnerability was due to an unauthorized backdoor embedded in the source code, enabling hackers to execute arbitrary PHP code remotely. The affected software, myBB, is a popular open-source forum software used by millions of websites worldwide. The gravity of this exploit lies in the fact that it requires no authentication, potentially leading to a full compromise of the web server under the context of the web application.
Vulnerability Summary
CVE ID: CVE-2011-10018
Severity: Critical (9.8/10)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Full compromise of the web server, potential system compromise or data leakage
Affected Products
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Product | Affected Versions
myBB | 1.6.4
How the Exploit Works
The exploit takes advantage of an unauthorized backdoor in the source code of myBB version 1.6.4. This backdoor allows attackers to execute arbitrary PHP code remotely by injecting payloads into a specially crafted collapsed cookie. This means that an attacker can manipulate the web server to execute malicious code without any authentication or user interaction. Since the vulnerability was introduced during the packaging process, it is not part of the intended application logic, making it difficult to detect without a thorough source code review.
Conceptual Example Code
Below is a conceptual example of how this vulnerability might be exploited. The attacker crafts a malicious payload and injects it into a collapsed cookie sent to the vulnerable server.
GET / HTTP/1.1
Host: target.example.com
Cookie: MYBB[COLLAPSED]=arbitrary_php_codeIn this example, `arbitrary_php_code` would be replaced with the attacker’s malicious PHP code. When the server processes the cookie, it executes the injected PHP code, leading to a potential full system compromise.
Recommended Mitigations
As a response to this vulnerability, it is imperative to apply the vendor-supplied patch to remove the backdoor from the source code. If immediate patching is not possible, implementing a Web Application Firewall (WAF) or Intrusion Detection System (IDS) may serve as a temporary mitigation. These solutions can help detect and block the execution of malicious PHP code sent through collapsed cookies, reducing the risk of server compromise.